Method for co-producing organic acid, xylose and lignin from lignocellulose

Abstract

The invention provides a method for co-production of organic acid, xylose and lignin from lignocellulose, and the method comprises the following steps: step 1, component separation is carried out on a lignocellulose raw material to obtain cellulose, xylose and lignin, and the component separation method adopts an alkali dissolution and acidification method and / or a solvent treatment method; 2, performing acid production fermentation on the cellulose in the step 1 to obtain an organic acid mixture; according to the method provided by the invention, xylose and lignin can be efficiently separated, the acid production steps are simple and controllable, and the acid production effect is good.

Description

Technical Field

[0001] The invention relates to the technical field of biochemical production, and more particularly to a method for co-producing organic acid, xylose and lignin from lignocellulose. Background Art

[0002] In order to achieve sustainable development of resources and alleviate the problem of continuous consumption of non-renewable energy, people are constantly looking for and developing biomass resources that can replace non-renewable resources. Green plants are the preferred biomass resources to be developed because they grow fast, are renewable, and have a large base.

[0003] Lignocellulose is mainly composed of hemicellulose, lignin and cellulose. Hemicellulose is a short branched heteropolysaccharide, which is used to produce xylitol. Lignin is a cross-linked phenolic polymer that can undergo oxidation, polycondensation and other reactions. It is used as an additive for epoxy resins, rubbers and thermoplastics, and is an important polymer raw material. Cellulose is a polymer of monosaccharide glucose covalently linked by beta-1,4 bonds, and is an important raw material for pulping, papermaking, textiles and chemical fibers. Lignocellulose is widely found in the stems, leaves and peels of plants. There are many materials containing lignocellulose that can be used, such as common agricultural crop residues, waste paper, herbaceous plants, wood, etc. It can be seen that it is of great significance to separate hemicellulose, lignin and cellulose from the above renewable biomass resources and make high-value utilization.

[0004] Lignocellulose is abundant and renewable. In recent years, people have also used lignocellulose as a raw material to prepare a variety of organic acids. For example, patent CN114032257A provides a method for co-producing lactic acid, xylitol and lignin from lignocellulose raw materials. This method pre-treats the lignocellulose raw materials and obtains a xylose-containing liquid phase and a cellulose- and lignin-containing solid phase by solid-liquid separation, wherein the solid phase containing cellulose and lignin is enzymatically hydrolyzed to obtain a glucose-containing liquid phase, and the glucose-containing liquid phase is fermented and purified to obtain lactic acid; patent CN109715816A provides a method for producing organic acids from lignocellulose raw materials, wherein the alkali liquor of a pulping plant is pre-treated to obtain a cellulose feed, the cellulose feed is enzymatically hydrolyzed to obtain a carbohydrate feed, and the carbohydrate feed is fermented by microorganisms to obtain organic acids. It is worth mentioning that in this invention, cellulose can be enzymatically hydrolyzed first and then fermented to obtain organic acids, or the enzymatic hydrolysis and fermentation processes can be carried out simultaneously, but it is necessary to reasonably adjust parameters such as raw materials, enzymes, microorganisms, and concentrations. Both of the above methods require the addition of enzymes to convert cellulose into glucose before fermentation to produce acid. The steps are cumbersome, the reaction system is complex and difficult to control, and is not suitable for industrial production. Summary of the invention

[0005] To solve the above problems, the present invention provides a method for co-producing organic acid, xylose and lignin from lignocellulose, which can efficiently separate xylose and lignin, and the acid production step is simple and controllable, and the acid production effect is good.

[0006] The object of the present invention is to provide a method for co-producing organic acid, xylose and lignin from lignocellulose, comprising the following steps:

[0007] Step 1, separating the components of the lignocellulose raw material to obtain cellulose, xylose and lignin, wherein the component separation is carried out by alkali dissolution and acid precipitation;

[0008] Step 2: fermenting the cellulose obtained in step 1 to produce acid to obtain an organic acid mixture.

[0009] Further, in step one, the alkali dissolution and acid precipitation method comprises the following steps:

[0010] (1) pretreating the lignocellulosic raw material by crushing and removing impurities, acid treatment, alkali treatment, steam explosion treatment or a combination thereof to obtain a pretreated material;

[0011] (2) washing the pretreated material and performing solid-liquid separation to obtain a liquid phase containing xylose and a solid phase containing cellulose and lignin;

[0012] (3) treating the solid phase containing cellulose and lignin with alkali to separate the solid and liquid to obtain a liquid phase containing lignin and a solid phase containing cellulose;

[0013] (4) washing the solid phase containing cellulose with water, separating the solid phase, and obtaining a cellulose wet material and a washing liquid containing lignin;

[0014] (5) The liquid phase containing lignin in step (3) and the water washing liquid containing lignin in step (4) are combined, and subjected to acid treatment, heat treatment, and solid-liquid separation to obtain a lignin wet material, and the lignin is dried to obtain lignin.

[0015] Preferably, the lignocellulose of the present invention comes from one or a combination of corn straw, rice straw, wheat straw, reed, corn cob or bean straw.

[0016] Preferably, in step (1), the crushing and impurity removal adopts a crushing and impurity removal equipment, which includes coarse crushing, impurity and iron removal, fine crushing, and dust removal stages.

[0017] Further, in step 2, the conditions for acidogenic fermentation are:

[0018] Batch fermentation, semi-continuous fermentation or continuous fermentation is carried out under anaerobic conditions; the pH of the acidogenic fermentation is 5-10; preferably pH is 5-7; the temperature of the acidogenic fermentation is 32-58°C; preferably 35-53°C; the C / N ratio is 20-60; preferably 30-40; the solid content is 2.5-15%; preferably 2.5-12%; the fermentation time is 2-50 days; preferably 7-21 days.

[0019] Preferably, the nitrogen source comes from one or a combination of NH4Cl, corn steep liquor, sludge, potassium nitrate and urea.

[0020] Preferably, the acid-producing fermentation of the present invention adopts an acid-producing microbial flora; preferably, the anaerobic fermentation acid-producing microbial flora enriched by the method provided in the patent application (application number 2023113103664) is adopted.

[0021] Specifically, the enrichment method of the anaerobic fermentation acid-producing microbial community includes the F1 stage to the F3 stage, that is, the reactor can be divided into the F1, F2 and F3 stages during the entire operation process, and the organic load of the straw is gradually increased in the three stages until it operates stably in the F3 stage. Among them, the F1 stage is the start-up stage of the reactor, and the solid content and load are low. The solid content and load are increased to enter the F2 stage. After the acid production in F2 is stabilized, the proportion of straw in the material is increased, the C / N ratio is increased, and the F3 stage is entered to adapt the bacterial community to the high C / N ratio straw material.

[0022] Specifically as follows:

[0023] F1 stage:

[0024] The operation time of the F1 stage is 80 to 120 days, preferably 100 to 110 days;

[0025] The inoculum source is added to the reactor, and nitrogen is introduced to exhaust the air and then the reactor is closed; after starting the reactor, no material is fed in or discharged for two days, and then the substrate is supplied under the condition of 0.4-0.6 g VTS / L / d organic load; wherein the TS value of the substrate is 4.8-5.4%; the VTS value is 4.0-4.4%; the C / N ratio is 18-22; the material can be fed in and discharged once every two days, and the hydraulic retention time of the reactor is 90-110 days; and the physical and chemical parameters of the reactor can be monitored once every four days.

[0026] Specifically, regarding the inoculation source:

[0027] The solid content of the inoculation source used in the present invention is ≤5%.

[0028] Furthermore, in order to inhibit the activity of methanogens, the inoculum source is preferably pretreated, and the pretreatment method is: heat-treating the inoculum source at 75-85°C for 0.5-1.2 hours, and adding a methane inhibitor with a final concentration of 4-6 mM. Preferably, the methane inhibitor is 2-bromoethanosulfophate (BES).

[0029] Furthermore, the inoculum source may include inocula from different sources; specifically, inocula from different sources may be selected from a mixture of anaerobic digestion sludge from grain sugar factories, anaerobic digestion sludge from restaurant waste, anaerobic digestion sludge from cellulose, anaerobic digestion sludge from glucose, and anaerobic fermentation acid production reactor sludge from fruit waste. Among them, the anaerobic digestion sludge from cellulose is preferably anaerobic digestion sludge from cellulose at high temperature or anaerobic digestion sludge from cellulose at medium temperature; the anaerobic digestion sludge from glucose is preferably anaerobic digestion sludge from glucose at high temperature or anaerobic digestion sludge from glucose at medium temperature. Specifically, the appropriate sludge type may be selected according to different reaction temperatures.

[0030] Furthermore, the inoculum source comprises inocula from different sources mixed according to the total solids concentration (TS), each type of sludge accounts for more than 10% of the total solids concentration (TS), and more preferably, the inoculum sludges from multiple different sources are mixed in equal proportions according to the total solids concentration (TS).

[0031] In specific operations, the inoculum source can be crushed with a blender and then filtered (for example, using 2-3 layers of gauze for filtration) to ensure that the solid content of the sludge at the start-up of the reactor is below 5%.

[0032] Specifically, regarding the substrate:

[0033] The substrate used in the present invention is a mixture of straw, kitchen waste and a nitrogen source substrate; in the F1 stage, the VTS ratio of the straw, kitchen waste and nitrogen source substrate in the substrate is preferably (0.8-1.2): (0.8-1.2): (0.8-1.2).

[0034] Furthermore, the source substrate can be a substrate conventionally used in the field, specifically, residual sludge from a sewage treatment plant can be used; currently, urban sewage treatment plants in my country use the activated sludge method to treat sewage, which produces a large amount of residual sludge, and the sludge treatment process is still immature. Using residual sludge from a sewage treatment plant as a nitrogen source substrate can reuse the sludge, which is environmentally friendly and cost-saving.

[0035] Furthermore, the straw may be selected from a combination of at least one or more of corn straw, rice straw, wheat straw, reed or bean straw.

[0036] Furthermore, the straw can be steam-exploded straw. The steam-exploded straw can be straw that has been conventionally treated with steam explosion in the art, or it can be prepared according to the following method: adding straw material and water into a sealed container, maintaining for a period of time (which can be several minutes), and then suddenly reducing the pressure to steam-explode the straw material, so that the connecting layer between hemicellulose and lignin is destroyed, so that more active groups of cellulose are exposed, which is more conducive to degradation.

[0037] Furthermore, the food waste may be common food waste, or homemade, such as a wet weight mixture of crushed fruits, vegetables, and grains.

[0038] Preferably, the substrate can be stored at low temperature (eg, 4° C.) and diluted to a target solid content when used.

[0039] Specifically, regarding the reactor:

[0040] The reactor used in the present invention can be a high temperature reactor or a medium temperature reactor. A conventional reactor in the art can be selected, such as a conventional mechanical stirring tank and the like. The stirring speed of the reactor can be 0 to 150 ppm to ensure uniform mixing of the materials.

[0041] Preferably, the pH value of the reactor is 5.5-6.0; the operating temperature of the high-temperature reactor is 50-55°C; and the operating temperature of the medium-temperature reactor is 35-40°C.

[0042] Furthermore, when the reactor is a high-temperature reactor, the cellulose anaerobic digestion sludge can be selected from cellulose high-temperature anaerobic digestion sludge, and the glucose anaerobic digestion sludge can be selected from glucose high-temperature anaerobic digestion sludge.

[0043] Furthermore, when the reactor is a mesophilic reactor, the cellulose anaerobic digestion sludge can be selected from cellulose mesophilic anaerobic digestion sludge, and the glucose anaerobic digestion sludge can be selected from glucose mesophilic anaerobic digestion sludge.

[0044] In specific practice, a semi-continuous fully mixed flow anaerobic fermentation acid production reactor system can be constructed, and a high-temperature reactor or a medium-temperature reactor can be used to enrich the high-temperature bacterial community and the medium-temperature bacterial community respectively.

[0045] F2 stage:

[0046] The operation time of the F2 stage is 50 to 100 days, preferably 75 to 90 days; the pH value of the reactor is 5.5 to 6.0; the feed solid content is adjusted to 8 to 12%, the organic load is increased to 0.8 to 1.2 g VTS / L / d, the substrate is supplied, the substrate TS is 9.8 to 10.5%, the substrate VTS is 8.0 to 8.5%, and the VTS ratio of straw, kitchen waste and sludge in the substrate is (0.8 to 1.2): (0.8 to 1.2): (0.8 to 1.2); the substrate C / N ratio is 18 to 22; the material can be loaded and unloaded once every two days; the hydraulic retention time of the reactor can be 90 to 110 days; and the operation is continued until it is stable.

[0047] F3 stage:

[0048] The operation time of the F3 stage is 120 to 200 days, preferably 165 to 185 days; the pH value of the reactor is 5.5 to 6.0; the feed solid content is kept unchanged in this stage (the feed solid content is kept at 8 to 12% in this stage), and the organic load is increased to 1.8 to 2.2 g The substrate is supplied at VTS / L / d, the hydraulic retention time is adjusted to 45-55 days, and the VTS ratio of straw, food waste and sludge in the feed is changed from (0.8-1.2):(0.8-1.2):(0.8-1.2) to (2.8-3.2):(1.8-2.2):(0.8-1.2), and the substrate C / N ratio is increased from 18-22 to 38-42; the substrate TS is 9.5-10%, and the substrate VTS is 8.0-8.6%; the material can be loaded and discharged once every two days; the operation is continued until it is stable; and the microbial flora in the reactor during the stable operation of the F3 stage is collected.

[0049] It is worth mentioning that the microbial flora of the reactor during the stable operation of the F3 stage is collected by taking the fermentation liquid, centrifuging it at 4°C for 10 minutes, removing the supernatant, and the precipitate is the flora. The enriched flora is used for the acidogenic fermentation of cellulose in the present invention.

[0050] Preferably, after acidogenic fermentation of cellulose, a fermentation broth containing an organic acid mixture is obtained, wherein the organic acid in the fermentation broth is a combination of lactic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, and isovaleric acid.

[0051] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention provides a method for co-producing mixed organic acids, xylose and lignin by using lignocellulose as a raw material to replace grain raw materials, and the composition and content of the acid in the mixed organic acid can be adjusted by controlling the acid production fermentation conditions. After pretreatment of lignocellulose as a raw material, no enzymatic hydrolysis is required, and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 The present invention is a flow chart of the co-production of organic acid, xylose and lignin using lignocellulose as raw material. DETAILED DESCRIPTION

[0053] The present invention is described in detail below in conjunction with specific drawings and embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the content of the present invention still fall within the scope of protection of the present invention.

[0054] The raw materials used in the examples, unless otherwise specified, are all disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0055] The sources of the sludge, kitchen waste and straw used in the embodiments of the present invention are as follows:

[0056] Anaerobic digestion sludge from grain and sugar factories: COFCO Biochemical (Chengdu) Co., Ltd.;

[0057] Anaerobic digestion sludge of restaurant kitchen waste: The anaerobic methanogenetic reactor stably operated by the Environmental Biotechnology Research Center of the School of Architecture and Environment of Sichuan University. The restaurant kitchen waste was taken from the student cafeteria of Sichuan University;

[0058] Cellulose high temperature anaerobic digestion sludge: The high temperature anaerobic methanogenic reactor stably operated by the Environmental Biotechnology Research Center of the School of Architecture and Environment of Sichuan University uses commercially available carboxymethyl cellulose as the carbon source;

[0059] Cellulose mesophilic anaerobic digestion sludge: The mesophilic anaerobic methanogenic reactor stably operated by the Environmental Biotechnology Research Center of the School of Architecture and Environment of Sichuan University uses commercially available carboxymethyl cellulose as the carbon source;

[0060] Glucose thermophilic anaerobic digestion sludge: The thermophilic anaerobic methanogenic reactor stably operated by the Environmental Biotechnology Research Center of the School of Architecture and Environment of Sichuan University uses commercially available glucose as the carbon source;

[0061] Glucose mesophilic anaerobic digestion sludge: The mesophilic anaerobic methanogenetic reactor stably operated by the Environmental Biotechnology Research Center of the School of Architecture and Environment of Sichuan University uses commercially available glucose as the carbon source;

[0062] Anaerobic fermentation acid production reactor sludge from fruit waste: The anaerobic fermentation acid production reactor stably operated by the Environmental Biotechnology Research Center of the School of Architecture and Environment of Sichuan University uses commercially available fruits (banana, watermelon, and orange mixed in a weight ratio of 1:1:1) as raw materials;

[0063] The wastewater plant residual sludge is the dewatered sludge from a municipal wastewater treatment plant in Chengdu;

[0064] Artificially prepared food waste is a mixture of bananas, oranges, cabbages and rice at equal wet weight after crushing;

[0065] Steam-exploded straw refers to steam-exploded straw, wherein the steam explosion treatment comprises: adding corn straw and water into a closed container, and maintaining the pressure at 1.7 MPa for 2 minutes, and then suddenly reducing the pressure to steam-explode the straw material.

[0066] Table 1 shows the TS and VTS data of inoculum and substrate from different sources.

[0067] Table 1

[0068]

[0069] In the embodiment, one high-temperature reactor (working volume 4 L) and one medium-temperature reactor (working volume 2.4 L) were prepared to enrich the bacterial flora suitable for high temperature and the bacterial flora suitable for medium temperature, respectively.

[0070] Example 1

[0071] This example is used to illustrate the enrichment method of microbial flora.

[0072] 1. Reactor construction

[0073] Preparation of inoculum source: In order to enrich the anaerobic fermentation and acid-producing microbial community, the anaerobic digestion sludge of grain sugar factory, the anaerobic digestion sludge of restaurant waste, the high-temperature anaerobic digestion sludge of cellulose, the high-temperature anaerobic digestion sludge of glucose and the anaerobic fermentation and acid-producing reactor sludge of fruit waste were mixed and used as the inoculum source; inocula from different sources were mixed in equal proportions (i.e., 1:1:1:1:1) according to the total solids (TS) concentration (TS and VTS of inocula from different sources are shown in Table 1).

[0074] Preparation of substrate: Steam-exploded straw, artificially prepared food waste (banana, orange, cabbage and rice were crushed and mixed with equal wet weight) and wastewater plant residual sludge were used as substrates. Different substrates were mixed in equal proportions according to the volatile total solids (VTS) concentration (TS and VTS of various substrates are shown in Table 1). The mixed substrates were stored at 4°C and diluted to the target solid content when used.

[0075] A high temperature reactor (working volume 4 L, named H) was prepared.

[0076] 2. Reactor startup and operation

[0077] The present invention starts up a high temperature reactor (H).

[0078] The whole operation process of the reactor is divided into F1, F2 and F3 stages. The organic load of straw is gradually increased in the three stages until it operates stably in the F3 stage. The operating conditions of the reactor in the three stages are shown in Table 2.

[0079] Days 0 to 105 are the F1 stage.

[0080] The startup and operation temperature of the high-temperature reactor is 53°C, the stirring speed is 100rpm, and the pH value is controlled at 5.5-6.0. According to TS, the inoculation source obtained by mixing inoculum sludge from various sources in equal proportions is crushed with a blender and filtered with 2-3 layers of gauze to ensure that the solid content of the reactor startup sludge is less than 5%. In order to inhibit the activity of methanogens, the startup sludge needs to be pretreated. The startup sludge is heat-treated at 80°C for 1 hour, and a methane inhibitor 2-bromoethane sulfonic acid (2-bromoethanosulfophate, BES) is added at a final concentration of 5mM. The pretreated mixed inoculum is injected into the working volume of the reactor, and the reactor is closed after nitrogen is introduced to exhaust the air to reach an anaerobic state. After starting the reactor, no material was added or removed for two days. After that, a substrate containing straw, food waste and sludge (TS: 5.2%; VTS: 4.1%; C / N ratio: 20) was supplied under an organic loading condition of 0.5 g VTS / L / d. The VTS ratio of straw, food waste and sludge in the substrate was 1:1:1. The material was added and removed every two days. The hydraulic retention time of the reactor was 100 days. The physical and chemical parameters of the reactor were monitored every four days.

[0081] Days 105 to 189 are the F2 stage.

[0082] During this stage, the hydraulic retention time was maintained at 100 days, the feed solid content was adjusted to 10%, the substrate TS was 10.3%, the substrate VTS was 8.2%, the VTS ratio of straw, food waste and sludge in the substrate was 1:1:1; the substrate C / N ratio was 20; the organic load was increased to 1g VTS / L / d; and the operation was continued until stability.

[0083] Days 189 to 368 are the F3 stage.

[0084] In this stage, the feed solid content was maintained at 10%, the organic load was increased to 2g VTS / L / d, the hydraulic retention time was adjusted to 50 days, the substrate TS was 9.7%, the substrate VTS was 8.3%, and the VTS ratio of straw, kitchen waste and sludge in the feed was changed from 1:1:1 to 3:2:1, which increased the proportion of straw, reduced the proportion of sludge, and increased the feed C / N ratio from 20 to 40. Continue to operate until stable.

[0085] The microbial flora of the reactor during the stable operation of the F3 stage was collected by taking the fermentation broth, centrifuging it at 4°C for 10 minutes, removing the supernatant, and the precipitated part was the flora.

[0086] Example 2

[0087] This example is used to illustrate the enrichment method of microbial flora.

[0088] 1. Reactor Construction

[0089] Preparation of inoculum source: In order to enrich the anaerobic fermentation acid-producing microbial community, the anaerobic digestion sludge of grain sugar factory, the anaerobic digestion sludge of restaurant waste, the mesophilic anaerobic digestion sludge of cellulose, the mesophilic anaerobic digestion sludge of glucose and the anaerobic fermentation acid-producing reactor sludge of fruit waste were mixed and used as the inoculum source; inocula from different sources were mixed in equal proportions according to the total solids (TS) concentration (TS and VTS of inocula from different sources are shown in Table 1).

[0090] Preparation of substrate: Steam-exploded straw, artificially prepared food waste (banana, orange, cabbage and rice were crushed and mixed with equal wet weight) and wastewater plant residual sludge were used as substrates. Different substrates were mixed in equal proportions according to the volatile total solids (VTS) concentration (TS and VTS of various substrates are shown in Table 1). The mixed substrates were stored at 4°C and diluted to the target solid content when used.

[0091] Prepare 1 mesophilic reactor (working volume 2.4 L).

[0092] 2. Reactor startup and operation

[0093] The present invention starts up a medium temperature reactor.

[0094] The whole operation process of the reactor is divided into F1, F2 and F3 stages. The organic load of straw is gradually increased in the three stages until it operates stably in the F3 stage. The operating conditions of the reactor in the three stages are shown in Table 2.

[0095] Days 0 to 105 are the F1 stage.

[0096] The startup and operation temperature of the mesophilic reactor is 37°C, the stirring speed is 100rpm, and the pH value is controlled at 5.5-6.0. According to TS, the inoculation source obtained by mixing inoculum sludge from various sources in equal proportions is crushed with a blender and filtered with 2-3 layers of gauze to ensure that the solid content of the reactor startup sludge is less than 5%. In order to inhibit the activity of methanogens, the startup sludge needs to be pretreated. The startup sludge is heat treated at 80°C for 1 hour, and a methane inhibitor 2-bromoethane sulfonic acid (2-bromoethanosulfophate, BES) is added at a final concentration of 5mM. The pretreated mixed inoculum is injected into the working volume of the reactor, and the reactor is closed after nitrogen is introduced to exhaust the air to reach an anaerobic state. After starting the reactor, no material was added or removed for two days. After that, a substrate containing straw, food waste and sludge (TS: 5.2%; VTS: 4.1%; C / N ratio: 20) was supplied under an organic loading condition of 0.5 g VTS / L / d. The VTS ratio of straw, food waste and sludge in the substrate was 1:1:1. The material was added and removed every two days. The hydraulic retention time of the reactor was 100 days. The physical and chemical parameters of the reactor were monitored every four days.

[0097] Days 105 to 189 are the F2 stage, during which the hydraulic retention time is maintained at 100 days, the feed solid content is adjusted to 10%, the substrate TS is 10.3%, the substrate VTS is 8.2%, the VTS ratio of straw, food waste and sludge in the substrate is 1:1:1; the substrate C / N ratio is 20; the organic load is increased to 1g VTS / L / d, and the operation is continued until stability.

[0098] Days 189 to 368 were the F3 stage, during which the feed solid content was maintained at 10%, the organic load was increased to 2 gVTS / L / d, the hydraulic retention time was adjusted to 50 days, the substrate TS was 9.7%, the substrate VTS was 8.3%, and the VTS ratio of straw, kitchen waste and sludge in the feed was changed from 1:1:1 to 3:2:1, increasing the proportion of straw, reducing the proportion of sludge, and increasing the feed C / N ratio from 20 to 40. Continue to operate until stable.

[0099] The microbial flora of the reactor during the stable operation of the F3 stage was collected. The specific collection method was as follows: the fermentation liquid was taken and centrifuged at 4°C for 10 minutes, the supernatant was removed, and the precipitated part was the flora.

[0100] Table 2 shows the operating conditions data of the reactor at different stages.

[0101] Table 2

[0102] F1 F2 F3 Substrate TS (%) 5.2 10.3 9.7 Substrate VTS (%) 4.1 8.2 8.3 VTS ratio of straw, kitchen waste and sludge in substrate 1:1:1 1:1:1 3:2:1 Substrate C / N ratio 20 20 40 Organic load (gVTS / L / d) 0.5 1 2 Residence time (d) 100 100 50

[0103] Example 3

[0104] This example is used to illustrate the method of obtaining an organic acid mixture, xylose and lignin using lignocellulose as raw material (see the specific process flow for details). Figure 1 ), comprising the following steps:

[0105] Step 1

[0106] (1) crushing and removing impurities from corn stalks, and impregnating the corn stalks with 2 wt % dilute sulfuric acid, wherein the amount of dilute sulfuric acid used is 5 times that of the dry corn stalks, impregnating for 20 min at room temperature, and then treating for 30 min at a pressure of 0.9 MPaG to obtain a pretreated material containing cellulose, xylose, and lignin;

[0107] (2) The pretreated material is washed with water at a solid-liquid ratio of 1:9 for 2 times, and then centrifuged to obtain a liquid phase containing xylose and a solid phase containing cellulose and lignin.

[0108] (3) The solid phase containing cellulose and lignin is subjected to alkali treatment using sodium hydroxide, the amount of which is 10% of the mass of the solid phase, the dry matter concentration of the cellulose and lignin treated with alkali is 15%, the temperature during the alkali treatment is controlled at about 50°C, the treatment time is 2 hours, the lignin in the solid phase is dissolved, and then centrifugation is performed for solid-liquid separation to obtain a liquid phase containing lignin and a solid phase containing cellulose.

[0109] (4) The solid phase containing cellulose is washed with water at a solid-liquid ratio of 1:7 for 3 times, and then centrifuged for solid-liquid separation to obtain a cellulose wet material and a washing liquid containing lignin.

[0110] (5) The lignin-containing liquid phase of step (3) and the lignin-containing water washing liquid of step (4) are combined and acid-treated. Sulfuric acid is used for acid treatment, and the amount of sulfuric acid used is 1.2 times the amount of sodium hydroxide used. The temperature of the acid treatment is controlled at about 40° C. and the treatment time is 2 hours. Lignin is precipitated, and then heated to 90° C. and maintained for 1 hour to aggregate the precipitated lignin into large particles. Vacuum belt filtration is then used for solid-liquid separation to obtain a lignin wet material, and the lignin wet material is air-dried to obtain lignin.

[0111] Step 2

[0112] The cellulose obtained in step 1 was subjected to acidogenic fermentation, and the bacterial community used was the bacterial community enriched in Example 2. The inoculation amount of the acidogenic fermentation was 2%, the temperature was 37°C, the total solid content was 7.5%, the pH was 6, the nitrogen source was NH4Cl, and the C / N ratio was 40. The fermentation was carried out for 8 days to obtain 31.64 g / L of an organic acid mixture, and the carbon conversion rate was 57%. Among them, high performance liquid chromatography analysis showed that 17.13 g / L of lactic acid, 10.87 g / L of acetic acid, 2.95 g / L of propionic acid, and 0.69 g / L of other volatile fatty acids such as butyric acid, isobutyric acid, valeric acid, and isovaleric acid were obtained.

[0113] Example 4

[0114] This example is used to illustrate the method of obtaining an organic acid mixture, xylose and lignin using lignocellulose as raw material (see the specific process flow for details). Figure 1 ), comprising the following steps:

[0115] Step 1

[0116] (1) Step 1: crush and remove impurities from corn stalks, and soak the corn stalks with 2 wt % dilute sulfuric acid, the amount of dilute sulfuric acid used is 5 times the dry weight of the corn stalks, soak for 20 min at room temperature, and then treat at a pressure of 0.9 MPaG for 30 min to obtain a pretreated material containing cellulose, xylose and lignin;

[0117] (2) The pretreated material is washed with water at a solid-liquid ratio of 1:9 for 2 times, and then centrifuged to obtain a liquid phase containing xylose and a solid phase containing cellulose and lignin.

[0118] (3) The solid phase containing cellulose and lignin is subjected to alkali treatment using sodium hydroxide. The amount of sodium hydroxide used is 10% of the mass of the solid phase. The dry matter concentration of the alkali treatment is 15%. The temperature during the alkali treatment is controlled at about 50°C and the treatment time is 2 hours to dissolve the lignin in the solid phase. The solid-liquid separation is then performed by centrifugation to obtain a liquid phase containing lignin and a solid phase containing cellulose.

[0119] (4) The solid phase containing cellulose is washed with water at a solid-liquid ratio of 1:7 for 3 times, and then centrifuged for solid-liquid separation to obtain a cellulose wet material and a washing liquid containing lignin.

[0120] (5) The lignin-containing liquid phase of step (3) and the lignin-containing water washing liquid of step (4) are combined and acid-treated. Sulfuric acid is used for acid treatment, and the amount of sulfuric acid used is 1.2 times the amount of sodium hydroxide used. The temperature of the acid treatment is controlled at about 40° C. and the treatment time is 2 hours. Lignin is precipitated, and then heated to 90° C. and maintained for 1 hour to aggregate the precipitated lignin into large particles. Vacuum belt filtration is then used for solid-liquid separation to obtain a lignin wet material, and the lignin wet material is air-dried to obtain lignin.

[0121] Step 2

[0122] The cellulose obtained in step 1 was subjected to acidogenic fermentation, and the bacterial community used was the bacterial community enriched in Example 2. The inoculation amount of the acidogenic fermentation was 2%, the temperature was 37°C, the total solid content was 10%, the pH was 6, the nitrogen source was NH4Cl, and the C / N ratio was 40. Under the conditions, fermentation was carried out for 8 days to obtain 39.8 g / L of an organic acid mixture with a carbon conversion rate of 54%. Among them, high performance liquid chromatography analysis showed that 21.21 g / L of lactic acid, 13.57 g / L of acetic acid, 3.95 g / L of propionic acid, and 1.1 g / L of other volatile fatty acids such as butyric acid, isobutyric acid, valeric acid, and isovaleric acid were obtained.

[0123] Example 5

[0124] This example is used to illustrate the method of obtaining an organic acid mixture, xylose and lignin using lignocellulose as raw material (see the specific process flow for details). Figure 1 ), comprising the following steps:

[0125] Step 1

[0126] (1) Step 1: crush and remove impurities from corn stalks, and soak the corn stalks with 2 wt % dilute sulfuric acid, the amount of dilute sulfuric acid used is 5 times the dry weight of the corn stalks, soak for 20 min at room temperature, and then treat at a pressure of 0.9 MPaG for 30 min to obtain a pretreated material containing cellulose, xylose and lignin;

[0127] (2) The pretreated material is washed with water at a solid-liquid ratio of 1:9 for 2 times, and then centrifuged to obtain a liquid phase containing xylose and a solid phase containing cellulose and lignin.

[0128] (3) The solid phase containing cellulose and lignin is subjected to alkali treatment using sodium hydroxide. The amount of sodium hydroxide used is 10% of the mass of the solid phase. The dry matter concentration of the alkali treatment is 15%. The temperature during the alkali treatment is controlled at about 50°C and the treatment time is 2 hours to dissolve the lignin in the solid phase. The solid-liquid separation is then performed by centrifugation to obtain a liquid phase containing lignin and a solid phase containing cellulose.

[0129] (4) The solid phase containing cellulose is washed with water at a solid-liquid ratio of 1:7 for 3 times, and then centrifuged for solid-liquid separation to obtain a cellulose wet material and a washing liquid containing lignin.

[0130] (5) The lignin-containing liquid phase of step (3) and the lignin-containing water washing liquid of step (4) are combined and acid-treated. Sulfuric acid is used for acid treatment, and the amount of sulfuric acid used is 1.2 times the amount of sodium hydroxide used. The temperature of the acid treatment is controlled at about 40° C. and the treatment time is 2 hours. Lignin is precipitated, and then heated to 90° C. and maintained for 1 hour to aggregate the precipitated lignin into large particles. Vacuum belt filtration is then used for solid-liquid separation to obtain a lignin wet material, and the lignin wet material is air-dried to obtain lignin.

[0131] Step 2

[0132] The cellulose obtained in step 1 was subjected to acidogenic fermentation, and the bacterial community used was the bacterial community enriched in Example 1. The inoculation amount of the acidogenic fermentation was 2%, the temperature was 53°C, the total solid content was 10%, the pH was 6, the nitrogen source was NH4Cl, and the C / N ratio was 40. The fermentation was carried out for 14 days to obtain 26.28 g / L of an organic acid mixture with a carbon conversion rate of 32%. Among them, high performance liquid chromatography analysis showed that 10.28 g / L of lactic acid, 12.63 g / L of acetic acid, 2.1 g / L of propionic acid, and 1.27 g / L of other volatile fatty acids such as butyric acid, isobutyric acid, valeric acid, and isovaleric acid were obtained.

Claims

1. A method for co-producing organic acid, xylose and lignin from lignocellulose, characterized in that: The steps include: Step 1, separating the components of the lignocellulose raw material to obtain cellulose, xylose and lignin; The component separation method adopts alkali dissolution and acid precipitation method; Step 2: ferment the cellulose in step 1 to produce acid to obtain an organic acid mixture.

2. The method for co-producing organic acids, xylose and lignin from lignocellulose according to claim 1, characterized in that: In the step 1, the alkali dissolution and acid precipitation method comprises the following steps: (1) pretreating the lignocellulosic raw material by crushing and removing impurities, acid treatment, alkali treatment, steam explosion treatment or a combination thereof to obtain a pretreated material; (2) washing the pretreated material and performing solid-liquid separation to obtain a liquid phase containing xylose and a solid phase containing cellulose and lignin; (3) treating the solid phase containing cellulose and lignin with alkali to separate the solid and liquid to obtain a liquid phase containing lignin and a solid phase containing cellulose; (4) washing the solid phase containing cellulose with water, separating the solid phase, and obtaining a cellulose wet material and a washing liquid containing lignin; (5) The liquid phase containing lignin in step (3) and the water washing liquid containing lignin in step (4) are combined, and subjected to acid treatment, heat treatment, and solid-liquid separation to obtain a lignin wet material, and the lignin is dried to obtain lignin.

3. The method for co-producing organic acid, xylose and lignin from lignocellulose according to claim 1, characterized in that: In step 2, the conditions of the acidogenic fermentation are: Anaerobic or batch, semi-continuous or continuous fermentation; and / or, The pH of the acidogenic fermentation is 5 to 10; preferably, the pH is 5 to 7; The temperature of the acidogenic fermentation is 32-58°C; preferably 35-53°C; C / N ratio is 20 to 60; preferably 30 to 40; Solid content is 2.5-15%; preferably 2.5-12%; The fermentation time is 2 to 50 days, preferably 7 to 21 days.

4. The method for co-producing organic acids, xylose and lignin from lignocellulose according to claim 3, characterized in that: The nitrogen source is one or a combination of NH4Cl, corn syrup, sludge, potassium nitrate and urea.

5. The method for co-producing organic acids, xylose and lignin from lignocellulose according to claim 1, characterized in that: In the step 2, the acid-producing fermentation adopts an acid-producing microbial flora, preferably an anaerobic fermentation acid-producing microbial flora.

6. The method for co-producing organic acids, xylose and lignin from lignocellulose according to claim 5, characterized in that: The anaerobic fermentation acid-producing microbial community is enriched by the following method, which includes the F1 stage to the F3 stage: F1 stage: The F1 phase runs for 80 to 120 days; The inoculum source is added to the reactor, and nitrogen is introduced to exhaust the air and then the reactor is closed; the solid content of the inoculum source is ≤5%; no material is fed or discharged for two days after the reactor is started, and then the substrate is supplied under the organic load condition of 0.4-0.6g VTS / L / d; the TS value of the substrate is 4.8-5.4%; the VTS value is 4.0-4.4%; the C / N ratio is 18-22; the substrate comprises a mixture of straw, food waste and a nitrogen source substrate; preferably, the VTS ratio of straw, food waste and nitrogen source substrate in the substrate is (0.8-1.2): (0.8-1.2): (0.8-1.2); the nitrogen source substrate is preferably residual sludge from a sewage treatment plant; the straw is preferably steam-exploded straw; the material is fed and discharged once every two days; the hydraulic retention time of the reactor is 90-110 days; F2 stage: The operation time of the F2 stage is 50 to 100 days; the feed solid content is adjusted to 8 to 12%, the organic load is increased to 0.8 to 1.2 g VTS / L / d, the substrate TS is 9.8 to 10.5%, the substrate VTS is 8.0 to 8.5%, and the substrate C / N ratio is 18 to 22; the VTS ratio of straw, kitchen waste and nitrogen source substrate in the substrate is preferably (0.8 to 1.2): (0.8 to 1.2): (0.8 to 1.2); the hydraulic retention time of the reactor is 90 to 110 days; F3 stage: The operation time of the F3 stage is 120 to 200 days; in this stage, the feed solid content is maintained at 8 to 12%, the organic load is increased to 1.8 to 2.2 g VTS / L / d, the hydraulic retention time of the reactor is adjusted to 45 to 55 days, and the VTS ratio of straw, kitchen waste and nitrogen source substrate in the substrate is preferably changed from (0.8 to 1.2): (0.8 to 1.2): (0.8 to 1.2) to (2.8 to 3.2): (1.8 to 2.2): (0.8 to 1.2), and the substrate C / N ratio is increased from 18 to 22 to 38 to 42; the substrate TS is 9.5 to 10%, and the substrate VTS is 8.0 to 8.6%; Collect the microbial flora in the F3 stage reactor.

7. The method for co-producing organic acid, xylose and lignin from lignocellulose according to claim 6, characterized in that: The inoculum source is pretreated, and the pretreatment method is: heat-treating the inoculum source at 75-85° C. for 0.5-1.2 hours, and adding a methane inhibitor with a final concentration of 4-6 mM; the methane inhibitor is preferably selected from 2-bromoethane sulfonic acid.

8. The method for co-producing organic acids, xylose and lignin from lignocellulose according to claim 6, characterized in that: The inoculum source comprises inocula from different sources; the inocula from different sources are selected from a mixture of anaerobic digestion sludge from grain sugar factories, anaerobic digestion sludge from restaurant waste, anaerobic digestion sludge from cellulose, anaerobic digestion sludge from glucose, and anaerobic fermentation acid production reactor sludge from fruit waste; Preferably, the cellulose anaerobic digestion sludge is selected from cellulose high-temperature anaerobic digestion sludge or cellulose medium-temperature anaerobic digestion sludge; and / or, Preferably, the glucose anaerobic digestion sludge is selected from glucose high-temperature anaerobic digestion sludge or glucose mesophilic anaerobic digestion sludge.

9. The method for co-producing organic acid, xylose and lignin from lignocellulose according to claim 8, characterized in that: The inoculation source comprises inocula from different sources mixed according to the total solid concentration, each type of sludge accounts for more than 10% of the total solid concentration, and more preferably is mixed in equal proportions according to the total solid concentration.

10. The method for co-producing organic acids, xylose and lignin from lignocellulose according to claim 8, characterized in that: The reactor is a high temperature reactor or a medium temperature reactor; Preferably, The pH value of the reactor is 5.5 to 6.0; and / or, The operating temperature of the high temperature reactor is 50-55°C; and / or, The working temperature of the medium temperature reactor is 35-40°C.

11. The method for co-producing organic acid, xylose and lignin from lignocellulose according to claim 10, characterized in that: When the reactor is a high-temperature reactor, the cellulose anaerobic digestion sludge is selected from cellulose high-temperature anaerobic digestion sludge, and the glucose anaerobic digestion sludge is selected from glucose high-temperature anaerobic digestion sludge; When the reactor is a mesophilic reactor, the cellulose anaerobic digestion sludge is selected from cellulose mesophilic anaerobic digestion sludge, and the glucose anaerobic digestion sludge is selected from glucose mesophilic anaerobic digestion sludge.

12. The method for co-producing organic acid, xylose and lignin from lignocellulose according to claim 1, characterized in that: The organic acid is a combination of lactic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid and isovaleric acid.

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